During the operation of waste incinerators the safe and reliable disposal of refuse and hazardous waste stands above all in the foreground. At first, attempts have been made to limit the emission of hazardous materials to avoid environmental damage. The increasing world-wide scarcity of energy reserves has finally led to consideration being given to utilizing the calorific value of incinerator feedstock as well as to optimizing the energy efficiency of the processes.
Most substitute fuel incinerators were hitherto equipped with boilers for making medium pressure steam (up to 60-bar). The need to limit pressure comes from the high-temperature corrosion increasingly taking place at steam temperatures above 370° C. to 400° C. with the materials employed. High-temperature corrosion can result in the steam superheaters having to be replaced after a short operation time of 3 to 12 months. So that the steam produced can also be sufficiently superheated the steam pressure must be limited to a maximum of 40 to 60 bar in such plants.
DE 19 15 852 [GB 1 260 131] describes a method in which a waste boiler produces saturated steam that is further superheated in a main boiler fired by fossil fuel together with the saturated steam of the main boiler that is also equipped with a vaporizer. Depending only upon steam pressure and steam temperature only ca. 15% to 40% of the combustion thermal output of the main boiler is required for the simple superheating of saturated steam from a substitute fuel plant. However, in the document cited a complete power plant with vaporizer is provided for superheating the saturated steam produced in the substitute fuel plant, a consequence of which is that the superheating plant is not connected as auxiliary plant to increase the energy efficiency, but as a main plant, which itself must be considerably larger than the substitute fuel plant.
A method is described in EP 0 593 999 A1 in which a vaporizer fitted in the boiler of an incinerator is charged with feed water by means of which high pressure steam is generated as saturated steam or wet steam that is passed out of the boiler and superheated in an external superheater and then transferred to a high pressure steam turbine for power generation. However, the method of steam superheating and the fuel used are not described in this document. In particular, the problem of the relationship between evaporator surfaces in the combustion plant and the superheater surfaces that serve as external superheater is not discussed.
From the publication “Studie zum Energiepotential von KVA in der Schweiz, Baudirektion Kanton Zürich, AWEL, Amt für Abfall, Wasser, Energie and Luft” of June 2005, the waste incinerator HR-AVI Amsterdam, Netherlands, currently under construction is described. When operational this plant will have a net electrical efficiency of 30%. The efficiency will be obtained by employing different measures for increasing the efficiency of the boiler and the measures detailed in the following for increasing the turbine thermal efficiency compared to waste incinerators currently operated:                reduction of the condensation pressure,        superheating of live steam to 440° C.,        live steam pressure of 130 bar,        reheating with live steam as is common practice in nuclear power plants,        multistage condensate preheating.        
The investment costs for the efficiency-optimized Project HR-AVI with 30% net electrical efficiency are ca. 20%-30% above the costs of conventional waste incinerators with 22%-26% net electrical efficiency. Owing to the optimization a very considerable increase in superheater corrosion is expected so that the corresponding crane installation for rapid exchange of the superheater bundle as an expendable part has been taken into consideration. The increased live steam temperature and the reheating have provided the greatest part of the measures for the increase in efficiency opposite conventional incinerator plants, that are, however, utilized fully with the measures specified in this publication.
For technical reasons nuclear power plants with moderator water as pressurized water or boiling water reactors cannot carry out any significant live steam superheating with the energy from nuclear fission. Only reheating with live steam can be carried out. However, with entire steam generation plants as external superheaters for nuclear power plants the energy fraction remaining for external superheating of saturated steam is so low that complete large scale power plants of dimensions comparable to the nuclear plant itself would be necessary.